Self-pulsing oscillator



March25, 1947. H. w. LORD 2,417,834

SELF-PULSING OSCILLATOR Filed Feb. 19, 1943 SOURCE OF RONIZIH SYNCH PU ln vntor z Harold W. Lord, b 41W His Attorney- Patented Mar. 25, 1947 NITD STATES 2,417,834 SELF-PULSING oscmLA'ron New York Application February 19, 1943,-Serial No. 476,371

This invention relates to pulse generatingcircults, particularly to such-circuits for use in connection with pulse transmitters and the like, and its object is to provide improved and eificient circuits of this character which are extremely simple in form and at the same time capable oi producing pulses of considerable power.

In accordance with my invention, a self-pulsing oscillating circuit is provided constituted essentially by a single electron discharge device arrangednot only as an oscillator-but also to feed back orsupply energy from its anode-cathode circuit to its control electrode-cathode circuit through a transformer and a pulse forming element, such as a transmission line section, connected in the control electrode-cathode circuit for determining the duration and shape of the pulse. My invention permits the operation of a selfpulsing oscillator in which the power required for pulsing is only a fraction of the total input power.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection withthe accompanying drawing in which the single figure is a diagrammatic representation of a self pulsing oscillator circuit embodying my invention.

The oscillator circuit illustrated in the drawing comprises an electron discharge device Ill having an anode ll, a cathode l2 and a control electrode It. In order to produce oscillations and to determine the frequency of the oscillations there is provided a tunable circuitof any desired type. In the drawing there is illustrated a modified' Hartley oscillatory circuit comprising the inductances l5 and I6 connected by a pair of series connected radio frequency bypass condensers. The condensers prevent radio frequency currents from flowing through the pulsing circuit. The combination of coils and condensers is shunted by avariable condenser 18. One side'of the circuit IQ is connected to the anode Ii and the other side of the tunable circuitisconnected to the control electrode 13. The midpoint between the condensers i1 is grounded. Any suitable bias for the discharge device may be used as, for example, the resistance! between the cathode l2 and ground. Anode potential is supplied from a suitable source, indicated by the plus and minus signs in the drawing. The circuit oscillates in a well kn'own'manner; thecoupling between the '13 Claims. (owed-ac) charge device E ii.

anode-'to catliode and control electrode-to-cathode circuits being suflicient to provide feedback.

The pulse generating circuit comprises the electron discharge device lo andalso a transformer 28, having windings 2i and/22, respectively, in shunt with the oscillator anode-cathode circuit and the oscillator control electrode-cath ode circuit, respectively, the winding .22 being oppositely poled with respect to the winding 2i. A condenser 23 is connected in series with the winding 21 and is of such a capacity as to provide a substantially open circuit for direct currents A, pulse forming and pulse determining elem'ent "26 is connected in series with the transformer winding 22 and a resistor 21 in a second control electro'de cathode circuit of the discharge device I0. The element-26 is a capacitive time delay network and preferably comprises a suitfable transmission line section, the' line section including a plurality of capacitors 28 and reac- "tances 29. The time element characteristics of such networks are well knownto those skill'edin the art. i

In operation of the circuit illustrated in'the drawing, let it be assumed that the circuit is not oscillating but that a small current is beginning to now in the anode-cathode circuit of the dis,-

Under this condition small potentials appear i'across the windings of pulse transformerit in the second anode-cathode circuit. By properly connecting the secondary winding 22, apositive potentialis impressed upon the control electrode i301 the discharge device it and thereby causes more anode current to flow which in turn produces more current in the winding 2! and therefore'more potential is impressed upon control electrode Hi from windirig22. This regenerative action contin'ues'at a very'rapid rate.

, Duringthe abovefdesc'ribe'd regenerative action, a portion of the anode supply potential appearsacross the transiormer'primary winding 2l and a corresponding positive potential is impressed by secondarywindi ng 22 upon-the control electrode circuit. Neai'ly all of the positive potential" thereon appears across resistor 21 and the pulse forming line 26. If the resistance of tially to zero.

resistor 21 plus the equavilent control electrodeto-cathode resistance of the discharge device It) is equal to the surge impedance of the transmission line 26, then half of the secondary voltage of the winding 22 appears across the transmission line 26 and half across the resistor 21 and the control electrode-to-cathode resistance of thedischarge device l0.

The potential thus impressed upon the transmission line 26 causes a wave to travel down the line which is reflected at the'open end of the line and travels back to the starting end' thereof in proper phase so that as the wave finishes its travel a voltage equal to all of the voltage applied by the secondary winding 22 across the transmission line 26 and the resistance loads constituted by the resistor21 and the control electrode-to-cathode resistance, appears across the line 25 in the form of a charge on each ca-. pacitor 28, of such polarity that a negative potential appears on the control electrode side of the line. Under this condition the potential upon control electrode l3 is reduced substan- The resulting increase in the anode circuit impedance of discharge device reduces the potential across the primary winding 2| and this decrease, through regenerative action, increases, in turn, the negative potential applied to the control electrode 13 from winding 22 until the discharge device is biased to and beyond cutoff, thus terminating the pulse.

It may be preferable to so proportion the transmission line 26 and the resistance 21 that slightly more voltage develops across the line than across the resistor in which case a negative voltage is reflected back and a more negative potential is applied to the control electrode.

At the end of the pulse the charge on the capacitors leaks all at a rate determined by the leak resistor 30 until the negative bias upon the control electrode i3 is sufiiciently reduced so that when a synchronizing potential is applied to the control electrode-cathode circuit another pulse will be initiated. The pulse cycle as above described may then be repeated indefinitely.

If it is desired that the pulse generating circuit be operated in a self-timing manner, the ungrounded end of the leak resistor 30 may be connected directly to the cathode l2 and the synchronizing source omitted, the pulse rate then being determinedby adjustment of the resistor 30.

The above described pulse generating circuit is substantially the same as that described and claimed in my copending application, S. N. 464,033, filed Oct. 31, 1942, and assigned to the same assignee as the present invention.

If the regenerative action of the pulse generating circuit is allowed to continue until the discharge device is driven to saturation a relatively low anode potential results. In order to maintain the anode potential sufficient for satisfactory oscillatory conditions in the oscillator portion of the .circuit, there is connected a voltage limiting discharge device, such, for example, as a glow tube 3|, in shunt with the primary winding 2| of of potential only by the amount required to produce satisfactory pulses. Accordingly, a greater current is conducted through the discharge device than if the anode potential is allowed to drift lower.

The regenerative action above described may also cause a considerable control electrode current to flow. In order to maintain the control electrode at a potential satisfactory for good oscillation it is necessary to provide means to insure that regeneration will not raise the control electrode potential sufiiciently to cause appreciable control electrode current to flow. For this purpose, there is provided means for limiting the control electrode voltage. In the illustrative form of my invention, this means takes the form of a unilateral device, such as a diode 32, the anode of which is connected to the control electrode end of the resistance 21 and the cathode of which is connected to the cathode 12. The cathode of the diode 32 is grounded for pulse frequency currents by a suitable condenser 33.

With the foregoing arrangement there is provided ample anode voltage and the correct control electrode voltage to insure oscillation during pulses.

The energy for blocking the control electrode circuit in order to terminate pulses, as described above, is supplied from the anode-cathode circuit to the control electrode-cathode circuit through the pulse forming network 26 which is entirely independent of the oscillator part of the circuit.

'In the usual pulse transmission system the repetition rate of the pulses is substantially different, usually many times less, than the frequency of the oscillating circuit. Hence the oscillator adjustments may be made independently of the pulsing adjustments. The reverse is also true, for the circuit will function as a pulser with the oscillator portion inoperative. This independence of pulsing circuit with respect to the oscillating circuit permits determination of the pulse width and the repetition rate of the pulsing circuit without regard to the oscillator adjustments and the shape of the pulse output from the oscillator is controllable by the pulsing elements of the circuit.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects. For example, the cathode of the diode 32 may be grounded or connected to ground through a variable resistance shunted by a condenser of such a capacity as to constitute a ground for pulse frequency currents. I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a pulse generating circuit energized from said source and including said discharge device, a circuit connected between said control electrode and said cathode, a second circuit connected between said anode and said cathode, regenerative means including a transformer having a secondary winding and a primary winding operatively associated with said last-named circuits, respectively, for supplying potentials from said second anodecathode circuit to said control electrode-cathode circuit, and voltage limiting means in shunt with said transformer primary winding for maintaining a relatively high potential on said anode during each pulse.

2. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a pulse generating circuit energized from said source and including said discharge device, said pulse generating circuit comprising a circuit connected between said control electrode and said cathode and a second circuit connected between said anode and said cathode, regenerative means including a transformer coupling said last-named circuits thereby to supply potentials from said second anode-cathode circuit to said control electrode-cathode circuit during each pulse period, and electric discharge means for limiting the control electrode-cathode voltage to a value which substantially prevents the flow of control electrode current due to pulse voltages.

3.. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillatory circuit including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a pulse generating circuit energized from said source and including said discharge device, said pulse generating circuit comprising a circuit connected between said control electrode and said cathode and a second circuit connected between said anode and said cathode, regenerative means including a transformer having a secondary winding and a primary winding operatively associated with said last-named circuits, respectively, thereby to supply potentials from said second anode-cathode circuit to said control electrode-cathode circuit, discharge means for limiting the control electrode-cathode voltage substantially to prevent the flow of control electrode current due to pulse voltages, and second discharge means for limiting the voltage across said primary winding to a predetermined value whereby the anode potential remains sufiiciently high during pulse periods to maintain oscillations in said oscillator.

4. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a pulse generating circuit energized from said source and including said discharge device, a circuit connected between sa d control electrode and said cathode and a second circuit connected between said anode and said cathode, regenerative means including a transformer operatively associated with said last-named circuits for supplying potentials from said second anodecathode circuit to said control electrode-cathode circuit during each pulse period, and meansfor limiting the control.electrode-cathode voltage to substantially prevent the fiow of control electrode current due to pulse voltages, said last mentioned means comprising unilateral means connected between said control electrode and said cathode.

5. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a

cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a pulse generating circuit energized from said source and including said discharge device,

conductive upon reflection by said transmission line of pulses applied through said transformer.

6. In combination, a direct current source, an oscillator circuit energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, a non-oscillatory square wave pulse generating circuit energized from said source and including said discharge device, said pulse generating circuit comprising an open-ended transmission line section connected in series with a resistor between said control electrode and said cathode and a second circuit connected between said anode and said cathode, and a transformer regeneratively coupling saidsecond anode-cathode circuitto said control electrode through said transmission line section, said coupling being so poled that upon initiation of oscillations in said dis charge device said transformer applies a positive pulse to said control electrode, said transmission line section reflecting said positive pulse in aiding phase relation thereby to apply a delayed negative potential to said control electrode and render said discharge device non-conductive.

7. In combination, a direct current source, an oscillator energized from said source and comprising an electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, and a pulse generating circuit energized from said direct current source in parallel circuit relation with said anode-cathode circuit, said pulse generating circuit including a capacitive time delay network connected to control the potential of said control electrode, thereby recurrently to render said discharge device conductive to generate oscillations at a repetition rate independent of the frequency of said generated oscillations.

8. In combination, a direct current source, an

oscillator energizedfrom said source and comprising an' electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, regenerative coupling'means between said control electrode and said anode-cathodecircuit independent of said oscillator coupling means, and a capacitive time delay network energized by said regenerative coupling means and coupled to said control electrode for rendering said discharge device non-coductive, a predetermined time after initiation of oscillations therein and independent of the frequency of said oscillations.

9. In combination, 'a' direct current source, an oscillator energized from said sourceand comprising an electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator'coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, regenerative coupling means between said anodecathode circuit and said control electrode independent of said oscillator coupling means, and a capacitive time delay network coupled to said control electrode and responsive to energization of said regenerative coupling means by initiation of oscillations in said discharge device for rendering said discharge device non-conductive a predetermined time after initiation of said oscillations.

10. In combination, a direct current source, an oscillator energized from said source and comprising an electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, and regenerative coupling means between said control electrode and said anode-cathode circuit independent of said oscillator coupling means, a capacitive time delay network energized by said regenerative coupling means and coupled to said control electrode for rendering said discharge device non-conductive a predetermined time after initiation of oscillations therein, and means for discharging said capacitive network, thereby to render said discharge device conductive a predetermined time after terminatiltn of conduction.

11. In combination, a direct current source, an oscillator energized from said source and com prising an electron discharge device having an anode, a cathode and a control electrode, an anode-cathode circuit for said discharge device, oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, regenerative coupling means between said anodecathode circuit and said control electrode independent of said oscillator coupling means, a nonoscillatory capacitive pulse forming network coupled to said control electrode and responsive to energization of said regenerative coupling means for rendering said discharge device non-conductive a predetermined time after initiation of oscillations therein, discharge means for said capacitive network arranged to render said discharge device conductive a predetermined time after termination of conduction, and means coupled to said control electrode for recurrently rendering said discharge device conductive.

12. In combination, a direct current source, an oscillator energized from said source and comprising an electron discharge device having an anode, a cathode and a control electrode, an

anode-cathode circuit for said discharge device,

oscillator coupling means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase 7 relation to support oscillations in said circuit, regnerative coupling means independent of said oscillator coupling means and including an openended transmission line section connected between said anode-cathode circuit and said control electrode, said transmission line being arranged by reflection to render said discharge device nonconductive a predetermined time after initiation of oscillations therein and independent of the frequency of said oscillations, discharge means for said transmission line arranged to render said discharge device conductive a predetermined time after termination of conduction, and timing means coupled to said regenerative means for recurrently rendering said discharge device conductive at a repetition rate independent of the period of oscillation.

13. In combination, a direct current source, an oscillator energized therefrom comprising an electron discharge device having an anode, a cathode, and a control electrode, said oscillator including an anode-cathode circuit for said discharge device and means for deriving from said anode-cathode circuit and supplying to said control electrode oscillatory energy in proper phase relation to support oscillations in said circuit, pulse generating means energized from said source and including a second circuit connected between said anode and cathode and a capacitive time delay network connected between said cathode and said control electrode, and means for coupling said second circuit and said time delay network, thereby to render said discharge device non-conductive a predetermined time after initiation of oscillations therein.

HAROLD W. LORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,213,398 Kircher Sept. 3, 1940 2,257,663 Albrecht Sept. 30, 1941 2,300,429 Meacham Nov. 3, 1942 1,531,633 Vennes Mar. 31, 1925 2,024,138 Armstrong Dec. 17, 1935 FOREIGN PATENTS Number Country Date 541,087 German Jan. 6, 1932 

